1. Field of the Invention
The invention relates to a novel process for the chemical etching of glass.
2. Description of the Related Art
The term xe2x80x9cetching of a glass slidexe2x80x9d refers to the action of rendering it translucent, without being transparent, by rendering one of its surfaces opaque. The result of this action is an extensive roughness with a depth of a few microns, which roughness, according to its height, results in different macroscopic appearances of the surface thus treated. The terms xe2x80x9csparkling etched glassxe2x80x9d, xe2x80x9cmatt etched glassxe2x80x9d, xe2x80x9copaque glassxe2x80x9d or xe2x80x9ctranslucent glassxe2x80x9d are then used.
Etching is generally carried out by sanding the surface, when it is large in size, by depositing a thin layer or by chemical attack. The latter process is more particularly employed on small surfaces or on objects with more or less complicated shapes. Chemical attack is often carried out using fluoride ions, the latter reacting with the silicon ions of the glass. The glass object is immersed, for a few seconds to a few minutes, either in a bath of concentrated hydrofluoric acid or in an acid bath comprising an initiator for fluoride ions, such as ammonium bifluoride. The glass is subsequently rinsed with water.
Examples of known compositions for etching glass include that disclosed in the German patent published under the number 1,596,961, which comprises hydrofluoric acid, ammonium hydrogen fluoride, subsequently known as ammonium bifluoride, and water, that disclosed in the British patent published under the number 1,276,550, comprising hydrofluoric acid, a water-soluble fluoride, such as ammonium bifluoride, and one or more aliphatic carboxylic acids comprising from one to three carbon atoms which are substituted or unsubstituted by radicals comprising one or more halogen atoms and/or one or more hydroxyl or amino groups, such as, for example, formic acid, acetic acid, propionic acid, monochloroacetic acid, trichloroacetic acid or glycolic acid, or the composition disclosed in the Soviet patent published under the number SU 1,675,244, comprising hydrofluoric acid, ammonium bifluoride, sodium fluorosilicate, potassium fluorosilicate and water. The combination of ammonium bifluoride and hydrofluoric acid makes it possible to improve both the efficiency of the chemical attack and the appearance of the etched glass obtained. On the other hand, it also induces the formation of ammonia, which, in order to meet European discharge standards, necessitates an additional treatment of the industrial effluents, which is expensive and difficult to carry out. The limits set by these standards vary from one river to another. However, it is accepted that a level of ammonia of less than or equal to 1 mg/dm3 constitutes an acceptable average value. In point of fact, it has already been shown that the discharge of acid etching baths results in local concentrations of ammonia in a river of up to 3 to 5 times the maximum standard allowed.
Attempts have naturally been made, in order to overcome this disadvantage, to replace the ammonium bifluoride with sodium bifluoride or potassium bifluoride. Examples of compositions without ammonium salt include that disclosed in the Japanese patent application published under the number 334,841/1995, which comprises hydrofluoric acid, potassium bifluoride and water, or that disclosed in the Brazilian patent application published under the number 85 01205, which comprises hydrofluoric acid, potassium bifluoride, sodium fluoride, oxalic acid, glycerol and baryta. However, these etching compositions are prepared with hydrofluoric acid.
In point of fact, hydrofluoric acid is dangerous to store and handle and it is relatively expensive. For these reasons, etching products are marketed which comprise hydrochloric acid instead of hydrofluoric acid. However, these formulations also comprise ammonium bifluoride.
In the French patent application filed on Dec. 16, 1999 and registered under the number 99 15,887, the Applicant Company has disclosed and claimed a composition, characterized in that it comprises:
(a)xe2x80x94from 20% to 99% by weight of potassium bifluoride,
(b)xe2x80x94from 1% to 80% by weight of at least one water-soluble polyvalent cation salt, and optionally one or more of the following compounds:
(c)xe2x80x94up to 15% by weight of ammonium bifluoride,
(d)xe2x80x94sodium bifluoride in a proportion by weight of less than or equal to that of potassium bifluoride, it being understood that, when it comprises both ammonium bifluoride and sodium bifluoride, the total amount of these two bifluorides never exceeds that of potassium bifluoride,
(e)xe2x80x94from 5% to 60% by weight and more particularly from 10% to 30% by weight of at least one water-insoluble filler chosen from inorganic or organic products which are stable in an acidic medium, for example baryta or barium sulphate, gypsum, insoluble fluorides, such as calcium fluoride, insoluble fluorosilicates, such as sodium fluorosilicate or calcium fluorosilicate, calcium phosphate, calcium sulphate, inorganic oxides, in particular iron, zinc or titanium oxides, sugars and their polymers, such as cellulose or its derivatives, lignin or starch, high molecular weight ethylene oxide polymers, propylene oxide polymers or butylene oxide polymers, fatty acids and their derivatives which are solid at room temperature or insoluble high molecular weight polymers and resins, and/or
(f)xe2x80x94from 0.2% to 6% by weight and more particularly from 1% to 2% by weight of one or more surface-active agents which are stable in an acidic medium, such as, for example, alkoxylated fatty alcohols, phosphate-comprising fatty alcohols, phosphate-comprising alkoxylated fatty alcohols, ethylene and propylene oxide copolymers, fatty amides or cationic surface-active agents or the fluorinated derivatives of the said surface-active agents, silicone-comprising or fluorosilicone-comprising surface-active agents.
This composition can more particularly comprise:
from 1% to 60% by weight, in particular from 5% to 30% by weight and more specifically from 10% to 25% by weight of at least one water-soluble polyvalent cation salt. The water-soluble polyvalent cation salt is generally a divalent cation salt or a trivalent cation salt and is more particularly a calcium salt, a magnesium salt, a zinc salt, an iron salt or an aluminium salt, such as, for example, manganese chloride, magnesium chloride, magnesium sulphate, calcium chloride, ferric chloride, alumina or a mixture of these compounds, and/or
from 40% to 80% by weight of potassium bifluoride.
This composition is generally provided in the form of a mixture of powders, in the form of granules, in the form of pellets or in the form of pebbles.
In this same French patent application, filed on Dec. 16, 1999 and recorded under the number 99 15,887, the Applicant Company has also disclosed and claimed:
a glass etching solution, characterized in that it is capable of being obtained by mixing between 0.1 kg and 5 kg and preferably between 0.5 kg and 5 kg of the composition as defined above per liter of water or per liter of an aqueous solution of one or more inorganic or organic acids, it being understood that the inorganic acid optionally present in the said aqueous solution before mixing with the said composition is not hydrofluoric acid, and
a glass etching solution, characterized in that it is capable of being obtained by mixing, simultaneously or successively, from 0.1 kg to 4.95 kg of potassium bifluoride and from 0.005 kg to 4 kg of at least one water-soluble polyvalent cation salt per liter of water or per liter of an aqueous solution of one or more inorganic or organic acids, it being understood that the inorganic acid optionally present in the said aqueous solution before mixing with the said bifluoride and the said cation salt is not hydrofluoric acid. The latter solution is obtained while optionally also adding sodium bifluoride in an amount per liter of water or of acidic solution of less than or equal to that of the potassium bifluoride or up to 0.75 kg and preferably at most 0.25 kg of ammonium bifluoride or of sodium bifluoride and of ammonium bifluoride, it being understood that the total amount of these two bifluorides is less than or equal to the amount of potassium bifluoride and that the amount of ammonium bifluoride added per liter of water or per liter of acidic solution is less than or equal to 0.75 kg and preferably at most 0.25 kg, and/or while also optionally adding
from 0.025 kg to 3 kg and more particularly from 0.05 kg to 1.5 kg of at least one water-insoluble filler, such as that described hereinabove, and/or while also optionally adding
from 10xe2x88x923 kg to 0.3 kg and preferably from 5xc3x9710xe2x88x923 kg to 0.1 kg of one or more surface-active agents which are stable in an acidic medium, such as those described hereinabove.
According to a specific aspect of this etching solution, the proportion of water-soluble polyvalent cation salt mixed is from 0.005 kg to 3 kg, more particularly from 0.025 kg to 1.5 kg and very particularly from 0.05 kg to 1.25 kg per liter of water or per liter of acidic aqueous solution. The water-soluble polyvalent cation salt or salts used are the same as those described for the dry composition.
According to another specific aspect of these two etching solutions, the proportion of potassium bifluoride salt mixed is from 0.2 kg to 4 kg per liter of water or per liter of acidic aqueous solution.
The aqueous solution of one or more inorganic or organic acids acting as base for the two etching solutions described hereinabove is chosen from aqueous hydrochloric acid, sulphuric acid, phosphoric acid, nitric acid, fluorosulphonic acid, citric acid, tartaric acid, oxalic acid, acetic acid, propionic acid or succinic acid solutions or one of their mixtures. It is preferably an aqueous hydrochloric acid solution.
These etching solutions can be in the form of a non-flowing paste, in which case they also comprise one or more thickening agents or binders which are stable to acids.
In the same French patent application filed on Dec. 16, 1999 and registered under the number 99 15,887, the Applicant Company has also disclosed and claimed:
a glass etching process, characterized in that the surface of the glass object is brought into contact for approximately 0.5 second to approximately 300 seconds with a etching solution as defined above and then the object is rinsed and then dried.
According to an alternative form of this process, the sequence of bringing into contact and then of rinsing is repeated several times, more particularly 2 to 4 times.
In point of fact, the Applicant Company has found that the rinsing with water, whether it is acidic or basic, of the object which has been subjected to the chemical treatment with the etching solutions described hereinabove is not sufficient to remove the thin potassium fluorosilicate film attached to the surface of the said object.
In accordance with the invention, provided is a process for etching glass objects by chemical treatment. The process comprises:
(a) at least one stage of etching by chemical treatment of the glass objects, and
(b) at least one stage of rinsing the etched objects of stage (a) with an aqueous solution of one or more alkali metal or alkaline earth metal cation salts.
The objects and aspects of the present invention will become apparent to one of ordinary skill in the art on a review of the specification and claims appended hereto.
A subject-matter of the invention is a process for etching glass objects by chemical treatment, characterized in that it comprises:
(a) at least one stage of chemical treatment of the glass object to be etched;
(b) and at least one stage of rinsing the glass object etched by the said treatment of stage (a) with an aqueous solution of one or more alkali metal or alkaline earth metal cation salts.
Stage (a) is carried out by bringing the object to be etched into contact with an etching solution for a period of time which depends on the nature of the etching solution, on the surface effect which it is desired to obtain and on the composition of the glass to be etched.
Generally, when the etching solution is based on potassium bifluoride and when contact is achieved by immersion of the object in the solution, the duration of the contact is between 0.5 second and 300 seconds.
Depending on their size, the process as defined above is carried out in order to etch one or more objects.
Stage (b) is carried out by immersion of the object to be rinsed in the saline solution for approximately 0.5 second to 300 seconds. If necessary, the solution is stirred during the rinsing.
A more particular subject-matter of the invention is a process as defined above in which the aqueous solution of one or more alkali metal or alkaline earth metal cation salts employed in stage (b) is chosen from aqueous sodium salt, lithium salt, calcium salt or magnesium salt solutions or from the aqueous solutions of a mixture of these salts and very particularly from aqueous sodium chloride, magnesium chloride, calcium chloride or magnesium sulphate solutions or from the aqueous solutions of a mixture of these salts.
The concentration of alkali metal or alkaline earth metal cation salts which are present in the aqueous solution employed in stage (b) is generally less than 20% by weight and it is preferably between 5% and 10% by weight.
According to a specific form of the process as defined above, the aqueous solution of one or more alkali metal or alkaline earth metal cation salts employed in stage (b) is a 10% by weight sodium chloride solution.
The aqueous solution of one or more alkali metal or alkaline earth metal cation salts employed in stage (b) can also comprise one or more surface-active agents chosen from alkoxylated fatty alcohols, phosphate-comprising fatty alcohols, phosphate-comprising alkoxylated fatty alcohols, ethylene and propylene oxide copolymers, fatty amides or cationic surface-active agents or the fluorinated derivatives of the said surface-active agents, silicone-comprising or fluorosilicone-comprising surface-active agents. In this case, the concentration of surface-active agents which are present in the aqueous solution employed in stage (b) is generally less than 20% by weight and is preferably between 0.5% and 5% by weight. It is preferable to employ anionic or cationic surface-active agents in the saline solution, such as, for example, lauryldimethylbenzylammonium bromide, sold under the name Amonyl(trademark) BR1244, or dioctyl sulphosuccinate, sold under the name Supermontaline(trademark) SLT 70.
According to a first alternative form of the process as defined above, the object which has been subjected to the treatment of stage (a) is subjected, during a stage (b0) , to rinsing with water, before being subjected to the treatment of stage (b).
Stage (b0) is carried out by immersion of the object to be rinsed in water and, if necessary, stirring the dipping bath or by spraying water over the object.
The water employed in stage (b0) can also comprise between 0.5% and 5% by weight of one or more surface-active agents chosen from alkoxylated fatty alcohols, phosphate-comprising fatty alcohols, phosphate-comprising alkoxylated fatty alcohols, ethylene and propylene oxide copolymers, fatty amides or cationic surface-active agents or the fluorinated derivatives of the said surface-active agents, silicone-comprising or fluorosilicone-comprising surface-active agents. It is preferable to employ anionic or cationic surface-active agents, such as, for example, lauryldimethylbenzylammonium bromide, sold under the name Amonyl(trademark) BR1244, or dioctyl sulphosuccinate, sold under the name Supermontaline(trademark) SLT 70.
The process or its alternative form as defined hereinabove can comprise a stage (b1) in which the object which has been subjected to stage (b) is rinsed with water. This stage (b1) can be followed, if necessary, by a stage (b2) of rinsing with demineralized water. If necessary or if desired, the stage (b) or the sequences of stages (b0) and then (b), (b) and then (b1), (b0), then (b) and then (b1), (b), then (b1) and then (b2) or (b0), then (b), then (b1) and then (b2) are repeated several times, more particularly 2 to 4 times.
In the process and its alternative form as described above, the objects can be drained for a few seconds on conclusion of a given stage before being subjected to the following stage, in order to improve the effectiveness of the said following stage.
According to a specific form of the process and of its alternative form as defined above, the glass objects which have been subjected to the treatment of stage (a) are drained for approximately from 10 to 60 seconds before being subjected to the first of the rinsing stages (b0) or (b). This draining stage then makes it possible to recover a non-zero amount of etching solution, which can optionally be reused.
According to another specific form of the process and of its alternative form as defined above, the sequence (a) and then (b), (a), then (b0) and then (b), (a), then (b) and then (b1), (a), then (b0), then (b) and then (b1), (a), then (b), then (b1) and then (b2) or (a), then (b0), then (b), then (b1) and then (b2), optionally including a draining stage inserted between one or more of the said stages (a), (b0), (b), (b1) and/or (b2), is repeated several times, more particularly 2 to 4 times.
An example of a etching solution appropriate for carrying out stage (a) is the aqueous solutions disclosed in the French patent application filed on Dec. 16, 1999 and registered under the number 99 15,887, the description of which forms an integral part of the present patent application.
These solutions are described hereinabove, in the paragraph setting out the state of the art.
The process as defined hereinabove is particularly appropriate for the etching of small glass objects, such as perfume bottles, liqueur bottles or bottles of wine or alcohol.
According to a final aspect of the present invention, a subject-matter of the latter is etched glass objects, characterized in that they are etched by the process as defined above.